Poly-a-olefin compositions containing di-
alkyl-j,j -thiodipropionates and a ni-
trogen containing compound



United States Patent POLY-a-OLEFIN COMPOSITIONS CONTAINING DI- ALKYL-3,3'-THIODIPROPIONATES AND A NI- TROGEN CONTAINING COMPOUND Clarence E. Tholstrup, Kingsport, Tenn., assignor to Eastman Kodak Company, Rochester, N.Y., a corporation of New Jersey N0 Drawing. Original No. 3,072,604, dated Jan. 8, 1963, Ser. No. 16,969, Mar. 23, 1960. Application for reissue Dec. 26, 1963, Ser. No. 340,702

16 Claims. (Cl. 260-4585) Matter enclosed in heavy brackets appears in the original patent but forms no part of this reissue specification; matter printed in italics indicates the additions made by reissue.

This invention relates to new poly-wolefin compositions. Preferred embodiments of the invention relate to polyethylene and polypropylene compositions having improved stability at elevated temperatures to oxidative degradation.

Poly-a-olefins such as polyethylene, polypropylene and the like are commonly subjected to elevated temperatures in the course of their processing into useful items of com merce. Such processing methods as rolling, injection molding, extrusion and the like at elevated temperatures usually result in oxidative [degration] degradation of the polymer. In addition, many uses of poly-a-olefins, such as in electrical insulation and the like, oftentimes expose the poly-wolefin to elevated temperatures. To minimize oxidative deterioration in poly-wolefins, antioxidants or stabilizers are oftentimes incorporated therein.

It is an object of this invention to provide new polywolefin compositions having improved resistance to thermal degradation.

It is another object of this invention to provide new synergistic combinations of stabilizers for poly-a-olefin compositions.

It is also an object of this invention to provide novel polyethylene and polypropylene compositions containing synergistic combinations of compounds that improve the stability of the polyethylene and polypropylene compositions against deterioration resulting from exposure to elevated temperatures.

Other objects of the invention wiil be apparent from the description and claims that follow.

The present invention com-prises poly-a-olefin composition having incorporated therein a stabilizer combination of a diester of 3,3'-thiodipropionic acid and a hydroxyl-containing amine.

The diesters of 3,3-thiodipropionic acid comprising the present stabilizer combinations have the following formula t l sicmcunion wherein R is an alkyl radical generally having 4 to carbon atoms, with 8 to 18 carbon atoms being preferred. A particularly effective ester has twelve carbon atoms for the R substituent, namely, dilauryl-3,3'-thiodipropionate. However, any diester of 3,3'-thiodipropionic acid as described above can be employed in the present stabilizer combination including the buty], amyl, hexyl, heptyl, octyl, nonyl, decyl, tridecyl, myristyl, pentadecyl, cetyl, heptadecyl, stearyl and eicosyl diesters of 3,3'-thiodipropionic acid, or mixtures thereof.

A wide variety of hydroXyl-containing amines can be effectively utilized in combination with the described diesters ol" 3,3'-thiodipropionic acid, as illustrated by those hydroxyl-containing amines or nitrogen-containing compounds having the formulas:

R OH

wherein R R R R R R R R, R and R are alkyl radicals having 1 to 18 carbon atoms, and preferably 1 to 12 carbon atoms; and wherein R is an alkyl radical or an alkoxy radical, both having 1 to 18 carbon atoms, and preferably 1 to l2 carbon atoms.

Typical hydroxyl-containing amines that can be suitably employed in combination with dialkyl-3,3'-thiodipropionates include:

4-hydroxy-4'-methoxydiphenylamine,

4-hydroxy-4'-isobutoxydiphenylamine,

4-hydroxy-4'-n-octyldiphenylamine,

3tert.-butyl-4'-hydroxydiphenylamine,

4-hydroxy-4-lauryldipheuylamine,

2-tert.-butyl-4-hydroxydiphenylamine,

4-hydroxy-4-stearyldiphenylamine,

3-stearyl-4'hydroxydiphenylamine,

2,6-di-tert.-butyl-p-dimethylaminomethylphenol,

2,6-dimethyl-p-distearylaminomethylphenol,

2,6-di-tert.-octyl-p-dilaurylaminomethylphenol,

2,6-distearyl-p-dimethylaminomethylphenol,

2,6-dilauryl-p-diethylaminomethylphenol,

N,N bis(2-hydroxy-3-tert.-butyl-5-methylbenzyl)methylamine,

N,N bis(2 hydroxy 3tert.-butyl-5-laurylbenzyl)laurylamine,

N,N bis(2 hydroxy 3 lauryl-S-stearylbenzyl)-n-butylamine,

N,N bis(2 hydroxy 3 stearyl-S-methylbenzyl)methylamine,

N,N bis(2 hydroxy 3 methyl-S-tert.-butylbenzyl)stearylamine,

N-acetyl-p-aminophenol,

N-n-butyryl-'p-aminophenol,

N-caprylyl-p-aminophenol,

N-pelargonyl-p-aminophenol,

N-myristoyl-p-aminophenol,

N-lauroyl-p-aminophenol,

N-palmitoyLp-aminophenol,

N-n-nonadecanoyl-p-aminophenol,

' and related hydroxyl-containing amines.

The combination of the described diesters of 3,3- thiodipropionic acid and hydroxyl-containing amines can be used to stabilize a wide variety of solid poly-a-olefin compositions against deterioration resulting from exposure to elevated temperatures. Any of the normally solid polymers of a-monoolefinic aliphatic hydrocarbons core taining 2 to 10 carbon atoms can be stabilized in accord ance with the invention. The subject stabilizer combinations are preferably used in polyethylene and polypropyl ene, particularly polypropylene, although such poly-a olefins as poly(3-methylbutene-1), poly(4-methylpentene- 1), poly(pentene-l), poly(3,3-dimethylbutene-l), poly- (4,4-dimethylbutene-l poly(octene-l poly(decene-l) and the like can also be stabilized with the subject stabilizer combinations. Both the so-called low density and high density" or high crystallinity poly-u-olefin compositions can be stabilized in accordance with the invention. Reference is made to Fawcett et a]. U.S. Patent No. 2,153,553 granted April 11, 1939, and to copending application Coover U.S. Serial No. 559,536 filed January 17, 1956, now abandoned, and Coover et al. U.S. Serial No. 724,904 filed March 31, 1958, now abandoned, with regard to the preparation of various poly-a-olefin compositions that can be stabilized against thermal degradation in accordance with the invention. The additive stabilizer combinations of the invention are especially useful for stabilizing the solid resinous poly-st-olefins having average molecular weights of at least 15,000 and more usually at least 20,000, although the stabilizer combinations of the invention can also be utilized to stabilize the so-called poly-a-olefin waxes having lower average moleeular weights of usually 3,000 to 12,000.

The amount of the combination of the diester of 3,3- thiodipropionic acid and the hydroxyl-containing amine employed in poly-a-olefin compositions in accordance with the invention can be widely varied. the stabilizing amount of this combination usually varying with the particular use to which the poly-m-olefin compositions are to be put. Concentrations of at least about 001% of each stabilizer component are suitable, although about 001% to 5% for each stabilizer component are generally used, with about 01% to 3% of the (liester of 3,3'-thio dipropionic acid and about 01% to 1% of the hydroxylcontaining amine being preferred, the concentration being based on the weight of the poly-a-olefin. [We] I generally utilize the combination of the subject stabilizers at a weight ratio of the diester of 3,3'-thiodipropionic acid to the hydroxyl-containing amine in the range of U100 to 100/1, and preferably 1/50 to 50/1.

The stabilizer combinations of the invention can be incorporated or blended into poly-a-olefin compositions by the conventional methods utilized for blending such materials into resins or plastics. Typical of such methods that can be suitably employed include milling on heated rolls, deposition from solvents, and dry blending. The stabilizers of the invention can be incorporated separately or together into the poly-a-olefin compositions.

The stabilizer combinations of the present invention lend to poly-rx-olefin compositions improved stability, and more particularly, improved stability against oxidative deterioration resulting from exposure to elevated temperatures. In addition, poly-a-olefin compositions containing the stabilizer combinations of the invention have enhanced stability against deterioration resulting from exposure to sunlight or ultraviolet light. Thus, poly-a-olefins stabilized in accordance with the invention have an extended life expectancy and can be used more effectively than unstabilized poly-a-olefins for a wide diversity of uses. Poly-a-olefins stabilized as described can be cast, extruded, rolled, or molded into sheets, rods, tubes, pipes, filaments and other shaped articles, including the widely used films of the polymers about .5 to 100 mils in thickness. The present compositions can be used for coating paper, wire, metal foil, glass fiber fabrics, synthetic and natural textiles or fabrics, and other such materials.

The subject stabilizer combinations of dialkyl esters of 3,3'-thiodipropionic acid and hydroxyl-containing amine are synergistic combinations, namely, the stabilizing effect of such combinations in polywolefins is substantially greater than the additive effect of the individual components of the combination.

The invention is illustrated by the following examples of preferred embodiments thereof. In the following examples the stability of the poly-a-olefins was determined by an oven storage test. The poly-a-olefin under investigation is compression molded into a smooth sheet or plate. The plate is then cut into pieces weighing about 0.25 g. each. The 0.25 g. samples of the molded polymer are then placed in an air oven at 160 C. Samples are removed at intervals and each sample analyzed for peroxides. The oven storage life is the time required for initial peroxide formation in a sample of the polymer. To determine peroxide formation in the oven exposed samples, each 0.25 g. sample in question is dissolved or suspended in 20 ml. of carbon tetrachloride and allowed to digest for 25 minutes. To this is added 20 ml. of a mixture consisting of glacial acetic acid and 40% chloroform, and then 1.0 ml. of a saturated aqueous solution of potassium iodide. The resulting mixture is allowed to react for two minutes, ml. of water is added to dilute the mixture, and then a starch indicator is added. The resulting mixture is then back-titrated with 0.002 N sodium thiosulfate. The peroxide concentration. P, in milliequivalents per kilogram of polymer is given by the expression, P=8S, where S is the number of milliliters of 0.002 N sodium thiosulfate used.

EXAMPLE 1 Several samples of powdered polypropylene were mixed with dilauryl-3,3-thiodipropionate and typical hydroxylcontaining amines of the invention, compression molded into plates /m inch in thickness, and the resulting molded samples evaluated with respect to stability by the 160 C. oven storage test described above. The polypropylene was a plastic grade solid polypropylene having an average molecular weight greater than l5,000, a density of about .91 and an inherent viscosity of about [.48 as determined in Tetralin at C. The results of the stability tests are summarized by the data set out in Table A below. Samples of the individual components of the various sta bilizer combinations in the polypropylene, as well as the polypropylene with no additive, were included in the stability test for purposes of comparison. In Table A. dilauryl-3,3-thiodipropionate is indicatcd as DLTDP. The concentrations in Table A are based on the weight of the polypropylene.

Table A Additive: Oven life at C. hours None 0.2 0.1% DLTDP l 0.05% 2,6-di-tert.-butyl-p-(dimethylaminomethyl)phenol 4 0.05% 2,6-di-tert.-butyl-p-(dimethylaminomethyl-phcnol+0.l% DLTDP 20 0.05% 3-tert.butyl-4-hydroxydiphenylamine 6 0.05% 3-tert.-butyl-4'hydroxydiphenylamine +01% DLTDP 0.05% N,N-bis(2-hydroxy-3-tert.-butyl-5-methylbenzyl)methylamine 4 0.05% N,N-bis(2-hydroxy-3-tert.-butyl-5-methylbenzyl)methylamine+0.l% DLTDP 25 average molecular weight greater than 15,000, a melt index of about 7.59 and a density of about .91 is substituted for the polypropylene, or if distearyl-3,3-thiodipropionate or di-n-octyl-3,3-thiodipropionate is substituted for the dilauryl-3,3'-thiodipropionate.

EXAMPLE 2 Other stabilizer combinations of the invention were evaluated by the method described in Example 1 in the stabilization of solid plastic grade polypropylene having an average molecular weight greater than 15,000, a density of about .91 and an inherent viscosity of about 1.25 as determined in Tetralin at 145 C. The results of the test are summarized by the data set out in Table B below. In Table B, dilauryl-3,3-thiodipropionate is indicated as "DLTDP. The concentrations in Table B are based on the weight of the polypropylene.

Table B Oven life at Additive: 160 C. hours None 2 0.3% DLTDP 3 0.05% 4-hydroxy-4-methoxydiphenylamine 12 0.05% 4 hydroxy 4' methoxydiphenylamine +03% DLTDP 60 0.1%-N-lauroyl-p-aminophenol 4 0.19 N lauroyl p aminophenol+0.3%

DLTDP 15 As observed from the data in Table B, diluaryl-3,3'thiodipropionate synergizes with hydroxyl-containing amines in polypropylene. Similar synergism is demonstrated if di-n-octyl-3,3-thiodipropionate or distearyl-3,3-thiodi propionate is substituted for the dilauryl-3,3'-thiodipropi onate. Such stabilizer combinations are likewise synergistic stabilizer combinations in polyethylene as demonstrated if solid plastic grade polyethylene having an average molecular weight greater than l5,000, a density of about .91 and a melt index of about 7.59 is substituted for the polypropylene.

As used herein, inherent viscosity (1 is calculated from the formula,

wherein C is the concentration of the polymer in grams per 100 cc. of Tetralin and 1 is the ratio of the viscosity of the solution of the polymer and Tetralin to that of Tetralin. The viscosities are determined at 145 C.

The present invention thus provides novel poly-a-olefin compositions having improved stability against deterioration resulting from exposure to elevated temperatures, and particularly, it provides novel synergistic stabilizer combinations for poly-a-olefin compositions.

Although the invention has been described in detail with reference to preferred embodiments thereof, it will be understood that variations and modifications can be effected within the spirit and scope of the invention as described hereinabove and as defined by the appended claims.

I claim:

[1. A solid poly-a-olefin composition comprising a solid pOly-a-Olefin prepared from an a-monoolefinic aliphatic hydrocarbon having 2 to 10 carbon atoms containing a stabilizer combination comprising at least about 001% by weight based on said poly-a-olefin of a diester of 3,3'-thiodipropionic acid having the formula a olefin of a nitrogen'containing compound selected from the group consisting of compounds having the formulas and wherein R is an alkyl radical having 4 to 20 carbon atoms, and about .00l% to 5% by weight based on said polya-olefin of a nitrogen-containing compound selected from the group consisting of compounds having the formulas RI! ,,:\\A f,' i/ no NH wherein R R R R R R R R R and R are alkyl radicals having 1 to 18 carbon atoms, and wherein R is selected from the grou consisting of alkyl radicals having 1 to 18 carbon atoms and alkoxy radicals having I to 18 carbon radicals] [3. A solid poly-a-olefin composition comprising solid polyethylene containing a stabilizer combination comprising about .001% to 5% by weight based on said polyethylene of a 3,3'-thiodipropionic acid having the formula it S(C HaCllgCOR),

wherein R is an alkyl radical having 8 to 18 carbon atoms, and about 001% to 5% by weight based on said polyethylene of a nitrogen-containing compound selected from the group consisting of compounds having the formulas and and

wherein R R R R R R R R R and R are alkyl radicals having 1 to 18 carbon atoms, and wherein R is selected from the group consisting of alkyl radicals having 1 to 18 carbon atoms and alkoxy radicals having 1 to 18 carbon radicals] [4 A solid poly-a-olefin composition comprising solid polypropylene containing a stabilizer combination comprising about 001% to 5% by weight based on said polypropylene of a 3,3'-thiodipropionic acid having the formula sttiticm om, wherein R is an alkyl radical having 8 to 18 carbon atoms, and about .001% to by Weight based on said polypropylene of a nitrogemcontaining compound selected from the group consisting of compounds having the formulas and ieNin rf wherein R R R R R R R R R and R are alkyl radicals having 1 to 18 carbon atoms, and wherein R is selected from the group consisting of alkyl radicals having 1 to 18 carbon atoms and alkoxy radicals having 1 to 18 carbon radicals] [5. A solid poly-a-olefin composition comprising solid polypropylene containing a stabilizer combination comprising about .O0l% to 5% by weight based on said polypropylene of dilauryl-3,3-thiodipropionate and about 001% to 5% by weight based on said polypropylene of a nitrogen-containing compound selected from the group consisting of compounds having the formulas and wherein R R R R R R R R R and R are alkyl radicals having 1 to 18 carbon atoms, and wherein R is selected from the group consisting of alkyl radicals having 1 to 18 carbon atoms and alkoxy radicals having 1 to 18 carbon radicals] [6. A solid poly-a-olefin composition comprising solid polypropylene containing a stabilizer combination comprising about 001% to 5% by weight based on said polypropylene of a diester of 3,3'-thiodipropionic acid having the formula o MCPHCHHHIORM wherein R is an alkyl radical having 8 to 18 carbon atoms and about 001% to 5% by weight based on said polypropylene of a nitrogen-containing compound having the formula (I lift 11 ;--Nt 1i rR wherein R is an alkyl radical having 1 to 12 carbon atoms] 7. A solid poly-ao-lefin composition comprising solid polypropylene containing a stabilizer combination comprising about .00l% to 5% by weight based on said polypropylene of a diester of 3,3-thiodipr0pionic acid having the formula s ctlicmc om, wherein R is an alkyl radical having 8 to 18 carbon atoms and about 001% to 5% by weight based on said polypropylene of a nitrogen-containing compound having the formula I) s triticniiion wherein R is an alkyl radical having 8 to 18 carbon atoms and about 001% to 5% by weight based on said polypropylene of a nitrogen-containing compound having the formula (III m wherein R R", R", R and R are alkyl radicals having 1 to 12 carbon atoms] 9. A solid poly-a-olefin composition comprising solid polypropylene containing a stabilizer combination comprising about 001% to 5% by weight based on said polypropylene of a diester of 3,3'-thiodipropionic acid having the formula 0 S(GJIICIII%ORlI wherein R is an alkyl radical having 8 to 18 carbon atoms and about .001% to 5% by weight based on said po]y propylene of a nitrogen-containing compound having the formula wherein R is selected from the group consisting of alkyl radicals having 1 to 12 carbon atoms and alkoxy radicals having l to l2 carbon atoms.

10. A solid poly-nt-olefin composition comprising solid polypropylene containing a stabilizer combination comprising 01% to 3% by weight based on said polypropylene of dilauryl3,3-thiodipropionate and 01% to 1% by weight based on said polypropylene of 4-hydroxy-4-melhoxydiphenylamine.

11, A solid poly-a-olefin composition comprising solid polypropylene containing a stabilizer combination comprising 01% to 3% by weight based on said polypropylene of dilauryl-3.3 thiodipropionate and .0191 to 1% by weight based on polypropylene of N-lat|roylpantinophenol.

12. A solid poly-a-olefin composition comprising solid polypropylene containing a stabilizer combination comprising .01 "/r to 3% by weight based on said polypropylene of dilauryl-3,3-thiodipropionate and 111% to 1% by weight based on said polypropylene of N,N-bist Z-hydroxy- 3-tert.-butyl-5-methylbenzyl)methylamine.

13. A solid poly-vt-olefin composition comprising solid polypropylene containing a stabilizer combination comprising .01 to 3 by weight based on said polypropylene of dilauryld,3'-thiodipropionate and 01% to 1% by weight based on said polypropylene of 3-tert.-butyl-4'-hydroxydiphenylamine.

14. A solid poly-a-olefin composition comprising solid polypropylene containing a stabilizer combination comprising 01% to 3% by weight based on said polypropylene of dilauryl-3,3-thiodipropionate and 01% to 1% by weight based on said polypropylene of 2,6-di-tert.-butylp--(dimethylaminomethyl)phenol.

15, A solid [70l}-tx-Ol'fill composition comprising a solid poly-alefin prepared from an ut-monoolefinic aliphatic hydrocarbon having 2 to carbon atoms containing a stabilizer combination comprising at least about .UOI% by weight based on said poly-a-olefirt of a diester of 3,3-tlzioi1ipropionic acid having the formula stclnclnirotti, wherein R is an alkyl radical horing 4 to 20 carbon atoms, and at least about .()0I% by weight based on said poly-wolefin of a nitrogen-containing compound selected from the group consisting of compounds having the formulas N-lauroyl'p-aminophenol and 18. A stabilizer combination comprising a tliestet' 0f 3,3-thiodipropionic acid having the formula 0 ll NHH'CIDCORM wherein R is an alkyl radical having 4 to 20 carbon atoms, and a nitrogen-containing compound selected from the group consisting of compounds having the formulas N-lanroyl-p-aminophenol and wherein R R R R R R R, R, R and R are olkyl radicals having 1 to 18 carbon atoms, and wherein R is selected from the group consisting of alkyl radicals having I to 18 carbon atoms and alkoxy radicals having 1 to 18 carbon. radicals, the weight ratio of said diester to said nitrogen-containing compound being in a range of 1/100 to IUO/l.

19. A stabilizer combination comprising dilauryl 3,3- thiodipropionate and 4-hydroxy 4' methoxydiphenylamine, the weight ratio of said thiodipropionate to said amine being in a range of 1/50 to 50/1.

207 A stabilizer combination comprising dil auryl 3,3- thiodipropionate and N-lauroyl-p-aminophenol, the weight ratio 0] said thiodipropionate to said amine being in a range of 1/50 to 50/1.

21. A stabilizer combination comprising dilauryl 3,3- thiodipt'OpiOttate and N,N-bis(2-hydroxy-3-tert.-butyl-5- methylbenzyl)methylaminc, the weight ratio of said thiodipropionate to said amine being in a range of 1/50 to 50/1.

22. A stabilizer combination comprising dilauryl 3,3- thiodipropionate and 3-terL-butyl 4' hydroxydiphenylamine, the weight ratio of said thiodipropionate to said amine being in a range of 1/50 to 50/1.

23. A stabilizer combination comprising dilauryl 3,3- tltiodipropionate and 2,6-di-tert.-butyl-p-(dimethylaminometh vI)-phenol, the weight ratio 0 said thiodipropionate to said amine being in a range of 1/50 to 50/1.

References Cited by the Examiner The following references, cited by the Examiner, are of record in the patented file of this patent or the original patent.

UNITED STATES PATENTS 2,101,879 12/1937 Strouse 260-571 2,448,799 9/1948 Happoldt et a1. 260-459 2,519,755 8/1950 Gribbins 260-4585 2,568,902 9/1951 Thompson et al. 260-4585 2,654,722 10/1953 Young 260-459 2,780,647 2/1957 Spiegler 260-571 2,802,810 8/1957 Bill 260-459 2,934,517 4/1960 Young 260-459 3,022,267 2/1962 Young 260-45.9 3,043,774 7/1962 COlTlel-[i 260-459 FOREIGN PATENTS 582,162 12/1959 Belgium. 890,468 2/1962 Great Britain.

LEON J. BERCOVITZ, Primary Examiner.

DONALD E. CZAJA, Examiner.

W. R. AUCHFUSS, Assistant Examiner. 

